The use of zeolites as catalysts and/or catalyst carriers has long been recognized and many methods to improve zeolitic base materials have been reported in the art. In the early days of zeolite research and development much attention has been devoted to physically changing the nature and possibly the properties of zeolitic base materials, e.g. by calcining under so-called selfsteaming conditions or by wet calcination. Also the treatment with ammonium-ions in various stages of the zeolite preparation procedures has been reported extensively.
It has also been reported that zeolites can be modified by treating them with certain metal salt solutions, or even with metal salts themselves, in combination with various pre- and after-treatments to ensure that the zeolites are produced in the most active form.
It has now been found that zeolites of the Y-type with interesting properties can be produced by modifying low alkali oxide-containing zeolites with certain metal salts followed by a calcination treatment. The zeolites thus prepared are of importance in the preparation of catalysts, in particular in the preparation of hydrocracking catalysts.